Biological specimens are often collected, transported and stored for analysis of the levels and concentrations of various analytes contained therewithin. Conventionally, liquid suspensions of biological specimens are stored in sealed airtight tubes under refrigeration. Liquid sample collection, handling, transportation and storage has many problems associated with it, for example: the cost of refrigeration (typically by dry ice) in remote collection centers; the risk of container breakage or leakage which causes loss of sample and the danger of infection; sample instability during shipment and storage; refusal of transport carriers to accept liquid biohazard shipments; and collection of adequate sample volume to ensure quantities compatible with laboratory methods of subsequent analyses. The costs of addressing the above problems are substantial.
Dried blood spot (DBS) and dried plasma spot (DPS) sampling on filter paper are alternative methods to the liquid sampling procedures, and have been used worldwide with some success. Since the 1980s, manufacturers such as Schleicher and Schuell Corp., Bio-Rad, Boehringer Mannheim Corp., and Whatman. Inc., have been producing filter papers for DBS and DPS sampling. In using these commercially available biological sampling filter paper systems, a blood or plasma spot is placed in one or more designated areas of the filter paper, allowed to dry, and then mailed along with a test request form to the laboratory. Commonly used filter papers are known to those of ordinary skill in the art, such as Whatman 3 MM, GF/CM30, GF/QA30, S&S 903, GB002, GB003, or GB004. Several categories of blotting materials for blood specimen collection are available, e.g., S&S 903 cellulose (wood or cotton derived) filter paper and Whatman glass fiber filter paper. However, certain disadvantages have been associated with these commercially available filter papers. Specifically, certain of these commercially available and commonly used materials lack characteristics which provide precision values and accuracy that are preferred for carrying out certain biological assays.
Genetic material can be extracted and isolated from DBSs in sufficient quantities for use in genetic analysis. For instance, DBS has been used for the detection of prenatal human immunodeficiency virus (HIV) infection by the polymerase chain reaction (PCR) (Cassol, et al., J. Clin Microbiol. 30 (12): 3039-42, 1992). DPS and DBS have also been used for HIV RNA detection and quantification (Cassol, et al., J. Clin. Microbiol. 35: 2795-2801, 1997; Fiscus, et al., J. Clin. Microbiol. 36: 258-60, 1998: O'Shea, et al., AIDS 13: 630-1, 1999; Biggar, et al., J. Infec. Dis. 180 1838-43, 1999; Brambilla, et al., J. Clin. Microbiol. 41(5): 1888-93, 2003); HIV DNA detection and quantification (Panteleefe, et al., J. Clin. Microbiol. 37: 350-3, 1999; Nyambi, et al., J. Clin. Microbiol. 32: 2858-60, 1994); and HIV antibody detection (Evengard, et al., AIDS 3: 591-5, 1989; Gwinn, et al., JAMA 265: 1704-08, 1991). HCV RNA detection and genotyping are also reported using DBS (Solmone et al., J. Clin. Microbio. 40 (9): 3512-14, 2002). Although these studies provide a good correlation with titers using DPS or DBS is obtained as compared with conventional liquid plasma samples, a loss of viral titers may occur after room temperature storage (Cassol, et al., J. Clin. Microbiol. 35: 2795-2801, 1997; Fiscus, et al., J. Clin. Microbiol. 36: 258-60. 1998). DBS and DPS samples are clearly less expensive and less hazardous to transport than liquid samples.
However, the procedure of analyte microextraction from DBS and DPS on filter paper suffers from a number of disadvantages. For example, the fibers and other components of the filters become dislodged into the reconstitution solution, and require further centrifugation separation and/or can impede the ability to isolate the genetic material, such as by blocking genetic material from adhering to a separation column. Such prior microextraction procedures require a high standard of technical assistance, and even then do not consistently provide results with a desired level of sensitivity and specificity. Moreover, reconstitution of DBS and DPS samples by conventional means results in dilution of the analyte of interest, as compared to its originally collected concentration in a fluid suspension, decreasing the sensitivity of any subsequent analysis.
Furthermore, the sample volume used for DBS and DPS on filter paper is limited, typically to 50 μl spots, and considerable difficulty in analyte detection can be encountered, particularly when the concentration of the desired analyte material is low in the sample. Also in the prior art, there is a lack of deliberate inhibition of enzymes and chemicals which degrade the analytes, such as genetic material contained therewithin. Even in the presence of a bacteriostatic agent there are conditions that permit enzymatic, nonenzymatic and autolytic breakdown of the genetic material. Furthermore, microextraction of genetic material from DBS or DPS on filter papers is considerably more difficult if absorption of high molecular weight DNA or RNA is required. Although the introduction of new material and transportation methods continuously improve the ways samples are handled, the quantity and quality of the sample available for subsequent analysis are still of great concern to researchers and clinicians alike.
Thus, there is a need for a safe, convenient and simple device for collection, storage and transportation of liquid suspension of biological specimens containing analytes of interest in a dry state, especially in large field studies and for application in settings where collection, centrifugation, storage and shipment can be difficult, as is often the case in developing countries. In addition, there is a need for improved recovery of the biological specimens for subsequent analysis that provides precision values and accuracy of detection of the analytes of interest contained therewithin.
Further, there is a need for a method for efficiently testing collected and stored blood resources for pathogens and other conditions which render a particular blood resource unsuitable for use in blood transfusion. As new pathogens and diseases are identified, blood resources (e.g., blood, plasma, blood cells, platelets, and other blood components) need to be re-screened for the presence of the pathogen or disease. Such a process is extremely expensive for organizations which store blood resources, such as blood banks and clinics. In order to avoid analyzing individual donor samples separately, blood banks will often test batches of samples together in a method known as “pooling.” Pooling involves combining individual samples into a common container, allowing the samples to mix, and then testing a volume of the mixed pool for the presence of an analyte of interest. If the substance is detected, individual samples from the pool are tested for the analyte.
One problem with current pooling methods is the loss of sensitivity caused by the dilution of the individual samples. If a sample contains the analyte of interest, the analyte will be diluted by a factor of x, where x equals the number of samples in the pool. For example, if an analyte is present in a sample at a concentration of 1 mg/ml and 10 samples are pooled, the analyte will be present in the pool at a concentration of 0.1 mg/ml. Because the analyte potentially can be diluted to a level lower than the threshold detection level (which would result in a false negative test result), regulatory agencies such as the U.S. Food and Drug Administration place limits on the quantity of samples that may be pooled in a batch. For example, a blood bank may be allowed to combine 8, 16, or 24 individual samples in a pool. Unfortunately, false negatives may be reported even when regulatory dilution limits are followed. The consequences of a false negative test report are substantial since the transfusion of a blood resource containing the pathogen, such as HIV, may infect the recipient. As such, it would be desirable to provide a method of effectively and efficiently screening biological resources such as for the presence of such a pathogen, disease, or condition without compromising the sensitivity of the screening.